(a) Field of the Invention
The present invention relates to a power train of a marine transport vessel, and more particularly, to a power train that can control a plurality of propellers with various speeds even if only one engine is adopted.
(b) Description of the Related Art
As is well known in the art, various kinds of marine transport vessels are used for transportation of passengers or cargo on water such as lakes, rivers, and oceans.
Such a marine transport vessel includes an engine for generating power and a transmission for transmitting the generated power to propellers. Usually, such an engine and a transmission are collectively called a power train. Hereinafter, the term “propeller” is used to include not only a conventional propeller for generating water current but also any rotating device for generating a reactive force to a body of the marine transport vessel. The term “marine transport vessel” is used to mean any marine vessel that moves by the reactive force of the propeller. In more detail, the marine transport vessel does not necessarily move on the water, but it may rather move under the water.
The transmission may be realized in a variety of forms, such as an automatic transmission or a manual transmission. However, a semi-automatic transmission described in Korean Patent No. 292325 (of which the filing no. is 10-1998-0063295) is very effective.
According to a conventional power train of such a transport vessel, an engine such as an internal combustion engine outputs power (i.e., torque) through one output shaft and a transmission that receives the output torque changes the rotational speed and then transmits it to a propeller. During such a power transmission, only one speed-ratio is realized.
According to such a conventional scheme of a power train, a power transmission pattern is very limited since the torque output from an engine having only one output shaft is changed by only one speed-ratio and is then transmitted to the propellers. That is, one engine can operate one or more propellers only at the same speed.
As a result, the behavior of a marine transport vessel is also limited. For example, for changing the direction of the vessel, rudders to the rear of the propellers are operated such that a direction of a reactive force is changed and thereby a torque for turning the direction of the vessel is generated. The turning radius of the vessel is consequently very large, as is well known in the art.
When such a turning radius of a vessel is reduced, various merits can be accordingly achieved. For example, the vessel may turn in a narrow region and accordingly interference between vessels may be minimized.
In order to provide different torques to different propellers, the vessel may adopt a plurality of engines and a plurality of transmissions respectively connected to the engines. However, in this case, torques of the separate engines are not easy to harmonize, and a large space is inevitably consumed by the engines and the transmissions.